From patchwork Fri Jan 15 21:10:37 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Chang S. Bae" X-Patchwork-Id: 41726 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 3E910398B162; Fri, 15 Jan 2021 21:15:22 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 3E910398B162 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1610745322; bh=d8pAdpt4Xtk+iSw2F2yNbSUMpaXbZh5W2q3w2ZIx61c=; h=To:Subject:Date:In-Reply-To:References:List-Id:List-Unsubscribe: List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To:Cc: From; b=gJpRtdDEHi/ihImflpg/nWsrhV8dAD4HtvDSp3vvefGF9tfwkk5By11vOOwcs5eHW Jbx586P3kK2Jvh1ceiSk512QtDQh2t51r9X009o4meMEHF1W/ZKbQD1MICadIrqCva cAY6wFtbRZ9L7XmyweaejXPskAE3Taf3scJ5+SLY= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from mga17.intel.com (mga17.intel.com [192.55.52.151]) by sourceware.org (Postfix) with ESMTPS id 6ADD33857C69 for ; Fri, 15 Jan 2021 21:15:20 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 6ADD33857C69 IronPort-SDR: enS/R9y87+ksm4o5i9tdaY4KXhfA4/AzrrIlYsGYmqckE6HPJgW11FtJlnoHUrS/Y+52acrU6g f5UE6kt2DsyQ== X-IronPort-AV: E=McAfee;i="6000,8403,9865"; a="158382275" X-IronPort-AV: E=Sophos;i="5.79,350,1602572400"; d="scan'208";a="158382275" Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Jan 2021 13:15:15 -0800 IronPort-SDR: n7CKBxPaxKjx3ZV66DcDZNB4rCprG6ugLaAR6/NGBPP3U0WkIxmg9lSdYhjcH8TYK8vmeXjFvC wymICGm5DwFg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.79,350,1602572400"; d="scan'208";a="401418973" Received: from chang-linux-3.sc.intel.com ([172.25.66.175]) by fmsmga002.fm.intel.com with ESMTP; 15 Jan 2021 13:15:15 -0800 To: bp@suse.de, tglx@linutronix.de, mingo@kernel.org, luto@kernel.org, x86@kernel.org Subject: [PATCH v4 3/4] x86/signal: Detect and prevent an alternate signal stack overflow Date: Fri, 15 Jan 2021 13:10:37 -0800 Message-Id: <20210115211038.2072-4-chang.seok.bae@intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20210115211038.2072-1-chang.seok.bae@intel.com> References: <20210115211038.2072-1-chang.seok.bae@intel.com> X-Spam-Status: No, score=-10.9 required=5.0 tests=BAYES_00, GIT_PATCH_0, KAM_DMARC_STATUS, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: "Chang S. Bae via Libc-alpha" From: "Chang S. Bae" Reply-To: "Chang S. Bae" Cc: linux-arch@vger.kernel.org, len.brown@intel.com, tony.luck@intel.com, libc-alpha@sourceware.org, ravi.v.shankar@intel.com, chang.seok.bae@intel.com, jannh@google.com, linux-kernel@vger.kernel.org, dave.hansen@intel.com, Borislav Petkov , linux-api@vger.kernel.org, Dave.Martin@arm.com Errors-To: libc-alpha-bounces@sourceware.org Sender: "Libc-alpha" The kernel pushes context on to the userspace stack to prepare for the user's signal handler. When the user has supplied an alternate signal stack, via sigaltstack(2), it is easy for the kernel to verify that the stack size is sufficient for the current hardware context. Check if writing the hardware context to the alternate stack will exceed it's size. If yes, then instead of corrupting user-data and proceeding with the original signal handler, an immediate SIGSEGV signal is delivered. While previous patches in this series allow new source code to discover and use a sufficient alternate signal stack size, this check is still necessary to protect binaries with insufficient alternate signal stack size from data corruption. Suggested-by: Jann Horn Signed-off-by: Chang S. Bae Reviewed-by: Len Brown Reviewed-by: Jann Horn Cc: Borislav Petkov Cc: Jann Horn Cc: x86@kernel.org Cc: linux-kernel@vger.kernel.org --- Changes from v3: * Updated the changelog (Borislav Petkov) Changes from v2: * Simplified the implementation (Jann Horn) --- arch/x86/kernel/signal.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c index 761d856f8ef7..91056a940271 100644 --- a/arch/x86/kernel/signal.c +++ b/arch/x86/kernel/signal.c @@ -242,7 +242,7 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size, unsigned long math_size = 0; unsigned long sp = regs->sp; unsigned long buf_fx = 0; - int onsigstack = on_sig_stack(sp); + bool onsigstack = on_sig_stack(sp); int ret; /* redzone */ @@ -251,8 +251,11 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size, /* This is the X/Open sanctioned signal stack switching. */ if (ka->sa.sa_flags & SA_ONSTACK) { - if (sas_ss_flags(sp) == 0) + if (sas_ss_flags(sp) == 0) { sp = current->sas_ss_sp + current->sas_ss_size; + /* On the alternate signal stack */ + onsigstack = true; + } } else if (IS_ENABLED(CONFIG_X86_32) && !onsigstack && regs->ss != __USER_DS &&